The cellular or tissue uptake of a molecule of interest such as, for example, a drug, a diagnostic agent, a probe or the like, can be enabled or enhanced by reversibly attaching the molecule of interest to a molecular transporter compound having guanidinium functional groups. The cellular uptake of the molecule of interest can be a function of the number and/or arrangement of guanidinium groups on the molecular transporter compound. A variety of guanidinium-rich (GR) molecular transporter compounds exhibit cell-penetrating activity, and branched (dendrimeric) GR molecular transporter compounds can carry a variety of biologically useful cargos into cells and into tissues. For example, GR peptides have been used to carry drugs into human skin and cells therein. In another example, GR dendrimeric molecular transporter compounds have been used for targeted therapy and imaging applications.
However, GR peptides and GR dendrimeric molecular transporter compounds can be difficult, time consuming, and expensive to synthesize. This in turn limits their applicability in basic research, imaging, and therapy. Simplified synthetic methods for making GR molecular transporter compounds can expand the range of applications of transporters in the delivery of drugs, drug candidates, probes and molecules of interest in chemotherapy, imaging, diagnostics, and mechanistic chemical biology.